Texas Instruments’ (TI) New Buck-Boost Converter Features 60nA Quiescent Current
The bidirectional DC/DC supports efficient charging of supercapacitor backups to extend the battery life of remote devices.
TI’s TPS61094 supports supercapacitor charging and discharging to support peak loads and backup power. It will also allow for what TI describes as “last-gasp communication” during a power outage. A bi-directional, synchronous buck/buck boost converter, the device features an internal bypass switch as illustrated in the diagram below.
Typical Application for the TPS61094. Image courtesy of datasheet
In quiescent mode, TI’s new TPS61094 draws a mere 60nA, only one-third of the current needed by competitive devices. It is primarily aimed at devices that are meant to run unattended on a single battery for extended periods of time. TI estimates that the new device can serve to extend battery life by as much as 20% in such applications.
Input and Output Voltages
Input voltage range is from 0.7V to 5.5V, with a 1.8V minimum required for start-up. Boost voltages (VOUT in the diagram) are programmable over a 2.7V to 5.4V range. Supercapacitor charging range is from 1.7V to 5.4V. The buck charging current is programmable over 2.5mA to 600mA range
The device features a 60nA quiescent current when the unit is operating in its buck charging mode or in its boost mode. In bypass mode, it draws a scant 4nA, and the bypass switch resistance is 100mΩ. The low side and high side MOSFETs feature RDS(ON)s of 60Ωm and 140Ωm, respectively. The TPS61094 switches at 1 MHz.
In total, the unit supports four operational modes, chosen by inputs to the MODE and EN pins. The TPS61094 features the safeguards expected by designers, including protection against output short circuit. It will also shut down if over-temperature occurs.
With VIN at 3V and VOUT at 3.6V, efficiency is specified at 92.3% with IOUT at 10μA. With IOUT at 100mA, efficiency jumps 96.3%
During automatic buck or boost mode, when the input power supply is applied the bypass switch is closed. This allows power to be directly applied to the output. That power is also used to charge the supercapacitor.
Also during automatic buck or boost mode, when the input power supply is disconnected or lower
than the output target voltage, the device enters boost mode and draws on the power reserves of the supercapacitor to maintain the specified output voltage.
There is also shutdown mode in which the load is completely shutoff from VIN. In forced bypass mode, VIN travels through the bypass switch to the load.
The TPS61094 serves applications that have to be on “standby” for long periods of time, saving battery power so as to be ready to spring into action when need be. Examples include:
- Energy harvesting
- Gas and water meters
- Portable medical equipment
- The TPS61094 is available in a 2-mm × 3-mm 12-pin WSON package
Getting to Market Faster
TI offers the TPS61094EVM-066 Evaluation Module to aid designers to more quickly understand and evaluate the TPS61094. By choosing the appropriate jumper combinations, the evaluation board can support four separate TPS61094 operating modes.